Growth in Boys with 45,X/46,XY Mosaicism: Effect of Growth Hormone Treatment on Statural Growth

45,X/46,XY mosaicism is a rare sex chromosome disorder of sex development. Short stature is a main feature of boys with this condition. Different causes likely contribute to growth impairment. Growth hormone (GH) has been administered to treat short stature in boys with 45,X/46,XY mosaicism, but conflicting data are available. Here, spontaneous growth patterns as well as short- and long-term follow-up studies during GH therapy in these patients are reviewed. Short- and mid-term data showed an improvement of the growth pattern in GH-treated boys, mainly when hormonal therapy was started early, while long-term follow-up demonstrated similar adult heights in GH-treated and untreated patients. Individual biological factors (e.g. different chromosome constitution, different mosaicism among various tissues, impaired pubertal growth spurt), non-homogeneous GH doses and different ages at start of therapy may contribute to the variable results. Thus, early GH therapy at pharmacological doses may improve the growth pattern of short boys with 45,X/46,XY mosaicism, but data on adult height are disappointing. Evaluation of larger patient samples treated by homogeneous doses and long-term follow-up studies assessing adult height and safety are needed to reach definitive conclusions on GH therapy in boys with 45,X/46,XY mosaicism.